Wear resistant metal body



n *L 5 R 7M, o /mm w m N 2 e 1MM Y .4 mw Y Rum ET El WMU .L O.M. MMM .wd/ .s W-Hd ..EM HRi RF A E w,

Aug. 4, 1936.

Patented Aug. ,l 4, 41936 UNITED STATES PATENT OFFICE l 3 Claims.

In Letters Patent of the United States No. 1,978,319, dated October 23, 1934, there is disclosed a method of making wear resistant metal castings which in use are subject to abrasion.

5 Observation of the continued use of stair treads and platforms formed in accordance with that method, particularly in and about the subway stations of New York city, has revealed that, while the stair treads and platforms so formed are highly satisfactory in providing safe tread for the traveling public and give long service even under the heavy duty imposed, it-is possible to give the treads and platforms much longer life than has been possible hitherto, while preserving their non-slipping quality. This is accomplished by forming the treads in accordance with the invention now to be described. The improved wear resistant castings are preferably made by the method described in said Letters Patent, but it will be understood, as this description proceeds, that the present invention is not limited to the making of the wear resistant castings by that method and is realized however the wear resistant particles are embedded in the surfaces of the metal body. In accordance with the invention the metal body is formed at its surface exposed to wear with heights or primary contact areas Aand intervening depressions or valleys or secondary areas and the vwear resisting particles are embedded not only in the surfaces of the heights or primary contact areas, but also in the surfaces of the depressed or secondary areas, It will be understood that thearrangernent of the primary or secondary areas or the design of the surface may be varied to'suit the conditions of use of the completed article. It will also be understood that while the present invention has been developed with particularvreference to the production of non-slipping surfaces subjected to the wear of other purposes such, for example, as a grinding or polishing device which is required to be wear resistant in a high degree..

In the accompanying drawing in which the invention is illustratedl Figure 1 is a plan view, somewhat diagrammatic, of a wear resistant mass adapted for use as a safe tread, the left hand portion of the gure representing the mass as rst formed, the middle portion representing the mass as somewhat worn down, and the right hand portion of the same figure representing the mass v'after it nhas been worn down further by continued wear.

Figure 2 is a view in section on the plane indicated by the broken line 2--2 of Figure 1.

human feet, the article produced may be used for In the embodiment of the invention chosen for illustration and explanation of its character, the main body a may be assumed to be of cast iron.

It is shown as having a checkered surface composed of heights or primary contact areas b and 5 intervening depressions or valleys or secondary areas c, which are preferably not angular in crosssection, but are somewhat flattened or obtuse in cross-section. When the article is formed numerous, relatively small, distributed particles of 10 Wear resistant material are embedded in the surfaces of the heights or primary contact areas, as Shown at d, and also in the bottoms and in the sides of the valleys, as shown at c; v

In the use of an article formed in accordance l5 with the invention the wear first comes on the heights or primary contact areas. After continued usethe heights are worn down. Before the development of the present invention when a tread, for example, was subjected to wear so 20 long continued that the tops of the primary contact areas were worn down below the embedded wear resistant particles, the tread as a Whole lost its non-slipping quality, but when 'a tread formed in accordance with the present inven 25 tion is subjected to use so long continued that the heights or primary contactfareas are worn downbelow the embedded particles of wear resistant material, the sides and bottoms of the interposed va11eys,'in which wear resistant 30 particles a're embedded, present wear resistant surfaces', as indicated in the middle and right of Figures 1 and 2 and it has been demonstrated that a safe tread constructed in accordance with the present invention continues to possess its 35 safety quality nearly twice as long as a tread of the same materials but formed with wear resistant particles only in the heights or primary contact areas.

satisfactory results are attained when the total areas of the heights of a tread are about equal to the total areas of the intervening valleys. .It will be understood that as to the representation of the embedded particles and the progress 45 of wear the drawing is diagrammatic or suggestive only and that the average size of particles and the depth to which they are embedded in the metal body will be determined in each instance by the requirements of the use to which the ar- 50 ticle is to be part.

I claim as my invention: 1. A metal body having a wear resistant surface, such metal body being formed with heights or primary contact areas and intervening Valleys It has been found in practice that generally 40 or secondary contact areas, and having numerous, relatively small, distributed particles of wear resistant'material embedded in the faces of the primary contact areas and also in the faces of the secondary contact areas.

2. A metal casting having a Wear resistant surface, such metal casting being formed with heights or primary contact areas and intervening valleys or secondary contact areas, and having numerous, relatively small, distributed particles of wear resistant material-embedded in the faces of the primary contact areas and also in the faces of the secondary contact areas.

3. A metal casting having a checkered surface, such metal casting 'being formed with heights or primary contact areas and intervening valleys or secondary contact areas. and having numerous, relatively small, distributed particles of wear resistant material embedded in the faces of the primary contact areas and also in the faces of the secondary contact areas.

HAROLD W. MOWERY. 

